Hydrochlorination of olefins



Jan.s,194s. w; N. AXE 2,434,094

' HYDRocHLoRInA'x-Ion op omsFIus Filed Sept. 8,v 1944 "am am( AUORNEM Patented Jan. 6, 1948 HYDROCHLORINATION F OLEFIN S William Nelson Axe, Bartlesville, Okla., assgnor to Phillips Petroleum Company, a corporation of Delaware Application September 8, 1944, Serial No. 553,241

7 claims. (c1. 1260-663) In one aspect, this invention relates to a novel process for the hydrochlorination of olenic hydrocarbons to produce alkyl chlorides. In another aspect, it is concerned with a no vel arrangement of equipment for carrying out such a reaction. Still more particularly it relates to the provision of a-method and means by which advantage is taken of countercurrent principles in effecting the interaction of aliphatic oleiins and hydrogen chloride in contact catalytic systems.

Alkyl chlorides represent a valuable group of organic intermediates that have long found application in the classical Wurtz-Fittig, Friedel-y Crafts and Grignard reactions. More recently alkyl chlorides have attained increasing importance as primary intermediates inthe production of alcohols, amines, mercaptans a'nd the like as a result of the abundant production of olefinic hydrocarbons in the petroleum industry. The displacement of expensivel alcohols by olefinic hydrocarbons .in hydrochlorination reactions has made possible large scale production of alkyl chlorides at economically attractive production costs with respect to raw materials consumed. More recently attention has been directed toward the development of more efficient and economical processing operations. Heretofore the hydrochlorination of olens has been accomplished in conventional equipment involving catalytic reactors, fractionating equipment and the like arranged in series such that the chemical raction, recovery of excess HCl, recovery of diluent and fractionation of the product are carried out in separate process units; x Thus, while some variations in the means of effecting the hydrochlorination itself have been described, relatively little improvement in subsequent process steps has been disclosed.

The principal object of the present invention is to provide an improved method and apparatus for effecting the hydrochlorination of .olefins to produce alkyl chlorides.

It is an object of this invention to provide a process for ,the hydrochlorination of olefins utilizing countercurrent principles.

A further o et/of resent invention is t0 effect the hydrochlorination of olef'lnic hydrocarbons over a solid contact catalyst under conditions such that hydrochlorination and primary segregation of alkyl chlorides are realized in the reaction unit. A

A still furtherobject is torprovide a. novel hydrochlorination reaction unit wherein a countercurrent flow of gaseous reactants and liquid/product is maintained.

Additional objects and advantages of the present invention will be apparent in the light of the subsequent disclosure. I

I have found that hydrochlorination of olefini hydrocarbons is efficiently and expeditiously carried out in a column-type reactor embodying a control.

and HC1 are removed from the product stream stripping column and a catalyst case. The novel reactor preferably includes a reboiler surmounted by a stripping section whichis in turn surmounted by a catalyst section filled with an adsorbent catalyst of coarse mesh. The olefin feed, prefx erably diluted with a selected inert hydrocarbon described more fully below is injected into the ycatalyst section where it contacts anhydrous HCl ascending the column from its point of introduction in the stripping section. Temperatures in lthe catalyst section are so controlled that the resultant alkyl halides remain in the liquid state and flow down the column While hydrocarbon vapors and HCl flow upwards against a stream of inert reflux liquid employed for temperature The physically dissolved hydrocarbon in the stripping section and substantially uncontaminated alkyl halides are continuously withdrawn fromfthe bottom of the column. Exit vapors at the top of the column comprise unreacted HC1 and hydrocarbon vapor.

In accordance with my invention,aliphatic oler?" fins are hydrochlorinated to make alkyl chlorides by a process which comprises continuously feed- -I ing hydrogen chloride into a vertical stripping zone, preferably equipped with fractionating plates or other inert means for effecting countercurrent contacting of vapor and liquid in the vmanner of fractional distillation, continuously feeding a mixture of the olefin and an inert condensible diluent into a verticalreaction zone superimposed on and in free fluid communication with the stripping zone and provided with a solid hydrochlorination catalyst. Preferably the olefin-diluent mixture is injected into the reaction zone at a plurality of vertically spaced points the olefin is caused to react so that no free olefin.

appears in either the bottoms or overhead product. A mixture of alkyl chloride, hydrogen chloride, any unreacted olefin and diluent descends from the reaction zone through the stripping zone and is fractionally distilled as it so descends in 'such manner so as to remove all olefin, hydrogen chloride and diluent. This is accomplished by the provision of a reboiling section at the bottom of stripping section and passing the conventional heating fluid therethrough. The hydrogen chloride is fed into the stripping section at a point an excess of HC1 over olefin is maintained and v other conditions are such that no polymerization takes place and the product is free from' any appreciable amounts of olefin polymer or other heavy by-products.

Conditions in the reaction zone are such that fractional distillation takes place therein facilitated by the granular solid catalyst which functions as av packing material to give ya packed column. A"v liquid phase and a vapor phase are always present in this section of the column and contact each other to give a rectifying action.

From the top of the reaction zone there is continuously 1withdrawn a vaporous overhead which in practice consists essentially of hydrogen chloride and diluent. Absence of other materials, especially unreacted olen, from this overhead is attributable to the avoidance of side reactions and the maintenance of conditions such that all of the lolefin is reacted with HC1 in the body of the column before it can attain the top of the column. This vaporous overhead is cooled to effect condensation of the diluent which is then passed in part as reflux to the top of the reaction column, the balance of the condensate being recycled as diluent to be injected into the catalyst zone with fresh olefin. From the reflux accumulator there is withdrawn a vaporous phase of hydrogen chloride which is recycled to the stripping zone after cooling and compression to remove hydrocarbons therefrom. The hydrogen chloride vapor.phase invariably contains some hydrocarbon and the liquid hydrocarbon phase contains an appreciable amount of dissolved HC1 but the separation obtained in the reflux accumulator is sufficiently good for the purpose at hand.

The reaction is conducted under anhydrous conditions which are maintained throughout the equipment. The olefin charge and diluent may be passed through a drier to effect removal of the last traces of moisture therefrom. Anhydrous hydrogen chloride is likewise employed. If desired, suitable drying means may be interposed in the lines which charge the diluent, olefin and the hydrogen chloride to the column.

The pressure at which the column is operated should be such that the diluent can be condensed to liquid phase at the operating pressure by means of ordinary cooling Water in order to avoidv expensive refrigeration requirements.

Preferably provision is made for individually adjusting the amounts of olefin and diluent fed into the several spaced points in the reaction zone in order to control to the desired extent conditions of concentration and to a lesser extent ternperature conditions.

A specific embodiment of the present invention involves the manufacture of butyl chlorides from a fraction of normal butylenes employing a solid catalyst such as aluminum chloride vadsorbed on a coarse granular carrier comprised of such materials as alumina, silica, bauxite, Porocel,- pumice and the like. ,Referring now to the accompanying simplified ow diagram, the reaction unit I6 is first described. The reactor is comprised of a cylindrical tower-like structure which is divided into three sections, namely: A, representing the catalyst zone;` B, representing a combined fractionating and stripping zone; Aand C, a reboiler zone. Zone A is filled with a solid catalyst of sufficiently coarse mesh as to permit easy up-flow of vapors and down-Iiow of liquid. The catalyst is supported on a perforated plate or screen which separates the zone A from zone B. Zone B may be provided with a suitable inert packing material such as ceramicware, raschig rings or it may be equipped with conventional bubble-plates. The only limitation in design is that the zone shall function with reasonable eflciency in separating product chlorides from olefin and diluent and that said section lmust cooperate with the operation of the reaction zone A. Zone C is merely a conventional reboiler equipped with a steam coil I1. The entire column operates substantially after the manner of a fractionating column. Reaction between the butylene feed and HC1 occurs in zone A with the formation of liquid alkyl chlorides which ow countercurrently with respect to HC1 and hydrocarbon vapors. Reaction temperature is controlled to a large extent by a reflux of inert diluent. The butyl chlorides along with unreacted olefin and diluent flow downward into zone B where ascending HCl and hydrocarbon vapors strip the hydrocarboncomponents from the product chlo-v rides. The kettle product from the reboiler is continuously withdrawn through line 33 as substantially pure butyl chloride while the overhead stream consists essentially of gaseous HCl and paraffinic hydrocarbon diluent.

One procedure for establishing operating conditions in tower I6 comprises the following sequence of steps: (1) charge the preferred diluent such as n-pentane to the column and establish fractionating conditions with liquid pentane in the reboiler and pentane vapor passing overhead with total reux return; (2) introduce HC1 from line I5 into the stripping zone B at a rate suitable for subsequent reaction purposes and establish substantial equilibrium between the input of line I5 and the output of line 21; 3) charge the predetermined olefin-pentane blend through manifold I3 into catalyst zone A in order to establish lthe downow of liquid butyl chlorides. By gradually increasing the heat input of coil I1, the diluent, is eventually displaced from zone C, at which time the unit is in condition for continuous withdrawal of alkyl chloride product via line 33.

Assuming the operating conditions have been established in the reaction column and referring now to the flow diagram, the operation of the process may be described in more detail. The olen feed stream is prepared by blending npentane diluent from tank I and line 2 with substantially undiluted normal butylenes from tank 3 and line 4. The volume ratio of diluent to olefin may vary with operating conditions, but for illustrative purposes it may be assumed that the two streams are blended in a 1:1 volume ratio. Oleiin and diluent pentane are thoroughly commingled in pump 5 and passed therefrom into heat exchanger II via line 6, valve 'I and -line 8 where the charge is preheated to a suitable temperature level which is determined by the temperature and pressure of the reaction zone. As an aid in precise temperature control of the reaction zone a portion or all of the feed may by-pass the heat exchanger by way of valve 9 and line IU; When desired, virtually any feed temperature may be maintained by appropriate manipulation of valves 'I and 9. The feed streams in lines 8 5 and I are recombined and discharged through pressure reducing Valve I2 into manifold I3 from which the feed is injected into the reaction zone A of comma ls at a pluranty of points. The heat 'of reaction liberated by the hydrochlorination rei in the vapor state through line I8. and the pene tane is condensed in I9 before flowing into reflux tank 20. A portion of the condensed diluent is returned to the top of the column through line 2l, pump 22 and line 23 to controlthe reaction temperature and to scrub any higherboiling material from the exit vapors. Diluent pentane in excess of rthat required for reflux is continuously returned to storage by way of line 24, pump 25 and line 26.

vHydrogen chloride is continuously metered to the stripping zone B from tank I4 and line I5 at such a rate that the mol ratio of HC1 to olefin is greater than 1:1 and usually is at least 2:1 ranging up to 3:1 though it may be even higher. The ascending HC1 serves as a stripping gas in zone B, aiding in the return of diluent and unreacted olefin to reaction zone B. The excess HC1 over that required for the hydrochlorination reaction leaves the column through line I8, condenser I9 and passes into reflux tank 20. The HCl being in the gaseous state is vented from tank 20 through line 21 which delivers it to com-` pre'ssor 28. Aftercompression to suitable storage pressures of from 200 to 700 p. s. i., the gas is passed through cooler 29 into a condensate trap 30 Where the last traces of hydrocarbon are removed via valve 3|. The compressed HC1 is then returned to storage tank I4 via line 3 2.

The successful operation of the present invention isnot confined to any specific catalyst composition, but may comprise any solid adsorbent catalyst of sufficient activity to promote hydrochlorination of olefins at temperatures below the boiling point of the product alkyl chlorides. Representative catalysts may include the4 halides of aluminum, iron and zinc, especially aluminum chloride, supported on porous s'olid `adsorbent carriers such as alumina, silica, bauxite and pumice.y Such aluminum chloride catalysts are l described in th'e following U. S. Patents; 2,277,-

512; 2,295,977; 2,311,713 and 2,313,053. An especially suitable carrier is the granular form of specially calcined bauxite known in the trade as PoroceL The vpresent hydrochlorination process is applicable to the preparation of any alkyl chloride of suiiicient stability to withstand fractional distillation at atmospheric or low superatmos'pheric pressures. Ordinarily it is preferred to operate the countercurrent column 4with aliphatic (acyclic) oleflns having from 2 to 6 carbon atoms per molecule, since chlorides derived from such olefins have been found to undergo substantially no decomposition at temperatures prevailing in the column reboiler.

Suitable diluents for use in this processare the diluent is condensibI at moderate pressurey and temperature so as to form reflux liquid for temperature control. Propane is a satisfactory diluent for pressure operations required in the hydrochlorination of ethylene and propylene. n-Butane is a satisfactory diluent for reactionsv involving propylene and higher olefins while npentane is a readilyavailable and suitable diluent in reactions employing butylenes and higher olefins. Selected, close-cut fractions of non-alkylatable natural gasoline mayotten be used advantageously. The diluent which is used-.functions both as a diluent and as a reflux liquid for the reaction column. v

Operating temperatures are preferably maintained below about 300 F. in order to avoid decomposition of the alkyl chloride products. Ordinarilyit is preferred to carry out the hydrochlorination within a temperature range of about 100 F.to about 300 F. The actual selection of a narrow temperature range within the Aabove limits will be dependent on the operating pressure and the particular alkyl chloride involved. Thus, in the preparation of ethyl chloride using propane as a diluent, a.suitable pressure is about 200 p. s. i. at which temperature propane boils at about 115 F. which approximately fixes the temperature of the reaction zone. At this pressure, ethyl chloride boils in the vicinity of 250 F., thus fixing the maximum reboiler temperature. On the other hand, in the preparation of amyl chlorides using n-pentane diluent at substantially atmospheric pressure, the reaction zone is maintained at about 96100 F. with a reboiler .temperature of about 22o-225 F.

In order to prevent appreciable polymerization of the olen feed, HC1 is fed to the column at such a rate as to give an HCl:olei-ln mol ratio in excess of 1:1 and preferably at least 2:1 ranging up to 3:1 or even higher.

From the foregoing it will be seen that the present invention provides a novel and unusually selected from normal parailinic hydrocarbons having boiling points appreciably below those of the product chlorides being synthesized.l Normal paraiiinsare preferable to isoparaflins since the latter might be alkylated. The diluent should boil suiciently below thev product alkyl chloride as to be lreadily completely separable therefrom in the stripping and reboiling sections. The normal parains are completely inert under the conditions prevailing in the operation. Preferably advantageous method of carrying out the hydrochlorination of oleiins. The equipment requirements are not excessive and the equipment is adapted to long life. The operation is simple and continuous and is easily controlled once the equipment has beenfbrought on-stream. Yields of product based on chemicals are excellent, loss ofv olefin being kept to a negligible figure. The product is exceptionally pure. y

Because of the well recognized thermal lability of alkyl halides, the presentv invention isv limited to products capable of withstanding reboiling at atmospheric pressure without undergoing decomposition. Since prolonged reboiling of those compounds falling within the scope of the invention is deleterious, excessive fractionation is avoided and a stripping gas is supplied to further minimize the need for long heating periods. The present invention further proposes to operate within such temperature limits that no appreciable vaporization of the product alkyl halides occurs. Another advantage is that the present invention effects very rapid removal by fractionation of the product alkyl halides from the reaction zone substantially immediately upon their formation. i

. .A marked .advantage of the'invention is that undesirable polymerization is prevented by reason of the maintenance of a molar excess of hydrogen chloride over olefin.`n Another advantage is that temperature `control is accomplished in a novel manner by the special use of a selected parafiinic diluent. Presence of unreacted hydrocarbon in the overhead from the reaction section is eliminated since complete reaction of the olefin is attained. The invention involves another advantage in that hydrogen chloride is fed into the stripping section Where it functions as a stripping gas and has ample time to become thoroughly distributed throughout the ascending vapors. Injection of the olefin feed at a multiplicity of points spaced in the direction of vapor flow provides for reactant concentrations favorable to hydrohalogenation and preventive of polymerization and at the same time distributes the exothermic heat of reaction evenly throughout the catalyst case. The presence of liquid oleiin in the catalyst zone is substantially prevented which further reduces any tendency to olefin polymerization. Numerous other advantages of the present invention will be apparent to those skilled in the art.

While the countercurrent process of the present invention has been described in considerable detail with certain specific illustrations,l variations in operating technique will be ap' parent to those skilled in the art; therefore, said speciiic illustrations are not to be construed as limiting the scope of the invention.

I claim:

1. In a continuous process for the production of alkyl chlorides by hydrochlorination of aliphatic olens, the improvement which comprises introducing hydrogen chloride into a vertical stripping zone in a vertical column, passing said hydrogen chloride as vapor upward through said stripping `zone and through a vertical reaction zone packed with solid catalyst material and above said stripping zone, introducing an olefin together with an inert diluent at a plurality of vertically spaced points into said reaction zone, reacting said olen and hydrogen chloride in the presence of said catalyst under conditions of temperature and pressure such that liquid and Vapor phases are present at all times, maintaining hydrogen chloride in molar excess over olen throughout said stripping and reaction zones, passing a liquid comprising alkyl chloride, residual unreacted olen and inert diluent downwardj--.

through said reaction and stripping zones, scrubbing the descending liquid with vapors containing excess hydrogen chloride in the manner of fractional distillation, reboiling the liquid attaining the bottom of said stripping zone, withdrawing a kettle product consisting essentially of alkyl chloride, and withdrawing a vaporous overhead consisting essentially of hydrogen chloride and inert diluent from the top of said reaction zone.

2. In a continuous process for the protection of alkyl chlorides by hydrochlorination of aliphatic olelns, the improvement which comprises continuously introducing hydrogen chloride into a vertical stripping zone in a vertical column, passing said hydrogen chloride as vapor upward through said stripping zone and through a vertical reaction zone .containing solid catalyst material and superimposed on said stripping zone, continuously introducing an olefin and an inert condensible diluent into said reaction zone, catalytically reacting said olefin and hydrogenchloride in said reaction zone under conditions Y of temperature and pressure such that liquid and vapor phases are maintained at all times, maintaining a molar excess of hydrogenV chloride over olefin throughout said stripping and reaction zones, passing a liquid comprising alkyl chloride,

residual unreacted olefin and inert diluent downward through said reaction and stripping zones,

scrubbing the descending liquid with vapors containing excess hydrogen chloride inthe manner of fractional distillation, reboiling the liquid attaining the bottom of said stripping zone, withdrawing a kettle product consisting essentially of alkyl chloride, withdrawing a vaporous overhead consisting essentially of hydrogen chloride and diluent from the top of said reaction zone, condensing the diluent contained in said overhead vapor, returning the resulting condensate to the top of said reaction Zone as reflux, and recycling hydrogen chloride vapor to said stripping zone.

3. The process of claim 2 wherein said hydrogen chloride and said olen are fed to said column in a m-ol ratio of HCl to olefin of at least 2:1,

4. The process of claim 2 wherein said reaction zone is maintained within a temperature range of to 300 F.

5. The process of claim 2 wherein said diluent is a normal parain hydrocarbon at least as heavy as propane and boiling suciently belowy'the product alkyl chloride to be readily and completely separable therefrom in the stripping and reboiling sections of said column.

6. The process of claim 2 wherein said olefin is normal butylene and wherein said diluent i, normal pentane. v

7. In a process for the catalytic hydrohalogenation of olefinic hydrocarbons in a combination reaction and purification system, the steps of charging an olefinic hydrocarbon of 2 to 6 carbon atoms in admixture with an inert hydrocarbon diluent int-o the catalyst section of said system, simultaneously charging gaseous hydrogen chloride into a stripping section of said system contignous to and below said catalyst section, contacting said olefin-containing and HC1 streams in said catalyst section to form liquid alkyl chlorides, permitting said alkyl chlorides to flow into said contiguous stripping section countercurrent to said HC1 stream, stripping unreacted olen and hydrocarbon diluent from said alkyl chlorides with the aid ofthe gaseous fI-ICl stream,.further stripping dissolved HC1 and REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,839 Hjerpe et al Jan. 23, 1934 2,204,172 Balear June 11, 1940 2,366,117 Leonard Dec. 26, 1944 1,985,457 Nutting et al. Dec. 25, 1934 2,099,480 Hjerpe et al Nov. 16, 1937 2,330,754 Skelton et al. Sept. 28, 1943 2,387,541 Sweeney Jan. 1, 1942 Certificate of Correction Patent No. 2,434,094. Jemiary 6, 194s.

WILLIAM NELSON AXE It 1s hereby certlfied that error appears 1n the printed specification of the above numbered patent requiring correction as follows: Column 7, line 56., for the word protection read production; and that the said Letters Patent 'should be read with this',v correction therein that the same may conform to the record of the case in the Patent Oice. 1

Signed and sealed this 13th day of April, A. D. 1948.

THOMAS F. MURPHY,

' Assistant Uommzssoner of Patents. 

